Advanced oxidation of refractory organics in leachate--potential methods and evaluation of biodegradability of the remaining substrate.

An assessment of potential methods suitable for degradation and/or reduction of refractory organics was performed on landfill leachate from SYSAV AB, Malmö, Sweden. Pretreatment of the leachate was performed in a sequence batch reactor designed for nitrification in activated sludge. Oxidation of the leachate was then O3, O3/pH adjustment (pH 9 and 10), H2O2, O3/H2O2 and performic acid in lab-scale reactors. The degradation of organic material was followed with chemical oxygen demand (COD) measurements for all experiments except for the performic acid treatment for which total organic carbon (TOC) measurements were used. The potential degradation of refractory organics into biodegradable organic material was analysed by subsequent oxygen uptake rate (OUR) measurements in laboratory batch reactors. Ozonation of biologically pre-treated leachate increased reduction of the organic material. The most biodegradable organic material was produced after oxidation with only ozone and ozonation at pH 9. Performic acid did not reduce the content of organic material in the leachate. However, a combination of biological pretreatment, chemical oxidation with O3/H2O2 and a subsequent biological process resulted in the most efficient oxidation method for the tested leachate